1. Field of the Invention
The present invention relates to electrical equipment. In particular, this invention relates to systems for detecting the state of electrical contacts in enclosed electrical equipment such as switchgears. More particularly, this invention relates to viewing the rotary knife blade contact earthing or grounding system in electrical equipment such as switchgears.
2. Description of the Prior Art
Switchgears are used in the electric power systems or grids and basically refer to the combination of disconnectors, fuses and/or circuit breakers used to isolate electrical equipment from the mains or alternating current (AC) electrical power supply. Switchgears are used to de-energize equipment to allow work to be done and to clear faults in the electrical equipment. This type of equipment is important because it is directly linked to the connectivity of the electricity supply.
The earliest central power stations used simple open knife switches, mounted on insulating panels of marble or asbestos. However, increasing power levels and voltages have made open manually-operated switches very dangerous to use for anything other than isolation of a de-energized circuit. By the early 20th century, a switchgear line-up was made up of a metal-enclosed structure with electrically-operated switching elements, using oil circuit breakers. Today, oil-filled equipment has largely been replaced by gas insulated equipment allowing large currents and power levels to be safely controlled.
High voltage switchgears were invented at the end of the 19th century for operating motors and others electric machines. The technology has been improved over time and is used with voltages up to 1,100 kV. However, until this date there is a need to manually view the contacts. Since it is tedious to view the contacts in an enclosed housing, and the result yielded by the sensors is not 100 percent guaranteed, there is a need for a manual mechanism to view the internal parts in the enclosed electrical equipment.
In case of gas insulated switchgears, the position of the switch and contacts cannot be viewed from the front side even if a front inspection window is provided due to its design restrictions. Further, it is not advisable to risk the life of workers during maintenance work if the state of the equipment cannot be properly determined. In the prior art, a cut-out was directly provided on the front side of the equipment to view the position of the contacts. However, such solution has not been successful due to the construction, position and design limitations. Further, variable case sizes and switch orientation has limited implementation of this technology. Also, the presence of gas within the housing further reduces visibility of the operator. In another arrangement, the position of the switch was changed to bring the earthing or grounding switch on top with linear motion contacts inside transparent glass insulation so that the position of the contacts can be seen clearly. However, this arrangement escalates the cost of the equipment due to the requirement of a new switch to meet such design changes.
German Patent No. 296 08 127 discloses endoscope devices wherein the endoscope devices are directly guided through guide tubes to the inspection windows of the switch panels, to be able to view the contact points arranged behind these inspection windows. The guide tubes of the switch panels are accessible from the front side, so that the operating personnel can directly manipulate the endoscope devices from the operating side of the switch panels.
The endoscope devices are equipped with an optical lens at their free end and also have a light source, allowing the contact areas arranged in the housings of the switch panels to be observed using these endoscope devices. At the same time, endoscope devices must be positioned in such a way that both the image segment and the image brightness are adequate to be able to assess the contact points with sufficient reliability.
Therefore, there is a need to view and provide illumination inside enclosed electrical equipment in a more efficient and cost effective manner.